JP2011106925A - Gas flow measuring instrument of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a gas flow measuring instrument of internal combustion engine, capable of improving the precision of gas flow measurements, without being affected by variation of the flow measuring value by turbulent flow and noise, and which is capable of improving the exhaust gas performance and fuel efficiency performance. <P>SOLUTION: The gas flow measuring instrument of the internal combustion engine equipped with a gas flow sensor 13 for detecting the gas flow rate, based on the amount of the heat discharge of a heat generating resistive element 30 calculates a flow rate differential value DQ, by differentiating the flow rate detection value detected by the gas flow sensor 13, and calculates a flow rate correction value Qec, which is obtained by correcting the flow rate detection value with a correction amount, according to the flow rate differential value DQ. Hence, the effect of the temporary flow rate variation due to turbulent flow and noise can be reduced; and even when the flow rate detection value Qes varies, a proper correction corresponding to the back flow amount can be performed, and precision of the flow measurement is improved. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to an exhaust gas flow rate of an internal combustion engine, and a gas flow rate measuring device that measures the flow rate of intake air and other gases, and in particular, correction means for reducing a flow rate measurement error when a reverse flow occurs due to pulsation of the gas flow rate. The present invention relates to a gas flow rate measuring apparatus.

  In internal combustion engines such as diesel engines, exhaust gas recirculation (EGR) is generally performed in order to reduce NOx and the like in the exhaust gas. In recent years, in order to sufficiently reduce NOx and PM (soot) in exhaust gas, it is required to control the flow rate of EGR gas and the flow rate of intake air with high accuracy.

  In recent years, EGR has been adopted in order to improve the fuel efficiency of gasoline engines, and it is necessary to improve the control accuracy of the EGR flow rate in order to satisfy both fuel efficiency and combustion stability.

  From such a background, a sensor (exhaust flow sensor) that directly measures the flow rate of EGR gas is arranged in the EGR passage, detects the flow rate of EGR gas, and controls the EGR valve so that the flow rate is suitable for reducing exhaust gas. An EGR control device that performs this is proposed in Patent Document 1 and the like.

  Here, the EGR passage is a gas flow path connecting the exhaust passage and the intake passage, and the exhaust gas in the EGR passage is supplied from the exhaust side according to the differential pressure between the exhaust pressure and the intake manifold pressure (intake pressure). Since it flows to the intake side, the flow rate (EGR flow rate) of the exhaust gas that actually flows through the EGR passage fluctuates (pulsates) due to the influence of the exhaust pressure fluctuation and the intake pressure fluctuation.

  For this reason, in an operation state in which the exhaust pressure fluctuation and the intake pressure fluctuation become large, the intake pressure may become higher than the exhaust pressure due to pulsation, and the EGR gas may flow backward to the exhaust side.

  The exhaust flow rate sensor as described in the above-mentioned document and the like is composed of a heating resistor (heat wire), and measures the gas flow rate by detecting the heat radiation amount of the heating resistor due to the gas flow.

  Since the hot-wire flow rate sensor generally cannot determine the gas flow direction, if a backflow of exhaust gas occurs due to pulsation, this is detected as a forward flow, and the flow rate of the exhaust gas is detected more than the actual flow rate. Detection accuracy is significantly reduced.

  The flow sensor that measures the air flow rate is highly responsive to the temperature distribution around the heating resistor due to the configuration that has a heating resistor formed of a thin film such as silicon and a temperature-sensitive resistor placed close to the upstream and downstream of the heating sensor. However, when the flow rate of exhaust gas is measured, it has been difficult to apply a thin film sensor due to the problem of heat resistance.

JP 2006-214275 A JP 2008-2833 A

  As described above, the flow rate measurement of exhaust gas has been proposed in Patent Document 1 or the like to apply a hot-wire flow rate sensor, but the responsiveness is insufficient with respect to the reverse flow due to pulsation, The flow direction cannot be detected. Therefore, there has been a problem that when the exhaust gas flows backward as described above, a flow rate measurement error occurs and the exhaust performance deteriorates.

 On the other hand, Patent Document 2 discloses a method of detecting and correcting the backflow of the hot wire type flow sensor by signal processing. In this document, since the second-order differential value of the flow rate measurement value peaks when backflow occurs, the period from when the second-order differential value of the flow rate measurement value increases until the second-order differential value increases again is the backflow period. And the measured flow rate is corrected by inverting the polarity of the flow rate measurement value during the backflow period.

 However, in the technique of Patent Document 2, when the flow rate measurement value fluctuates due to turbulence or noise around the heating resistor of the hot wire flow sensor, the second-order differential value of the flow rate measurement value fluctuates and the backflow period is erroneously determined. There was a case. If the reverse flow period is erroneously determined, the polarity of the flow rate measurement value during that time is reversed, so that the flow rate measurement error increases.

  The gas flow rate measuring device of the present invention relates to a gas flow rate measuring device for measuring the flow rate of exhaust gas of an internal combustion engine and the flow rate of intake air and other gases, and the gas flow rate measuring device provided with a flow sensor composed of a heating resistor. Therefore, even if there are fluctuations in the flow measurement value due to turbulent flow and noise around the heating resistor, the flow measurement error can be reduced by reducing the flow measurement error due to the reverse flow during pulsation, thereby improving the exhaust gas performance of the engine, The purpose is to improve fuel efficiency.

  The gas flow rate measuring device for an internal combustion engine of the present invention that solves the above-mentioned problems is a gas flow rate sensor for an internal combustion engine that includes a gas flow rate sensor that detects a gas flow rate based on a heat release amount of a heating resistor. The flow rate detection value of the gas detected by the above is differentiated to calculate a flow rate differential value, and the flow rate detection value is corrected by a correction amount corresponding to the flow rate differential value.

  According to the gas flow rate measuring apparatus for an internal combustion engine of the present invention, the flow rate detected value of the gas detected by the gas flow rate sensor is differentiated to calculate the flow rate differential value, and the flow rate detected value is corrected by the correction amount corresponding to the flow rate differential value. Therefore, it is possible to reduce the influence of temporary flow rate fluctuations due to turbulence and noise. Therefore, even when the flow rate detection value fluctuates, there is no malfunction of correction, appropriate correction according to the reverse flow rate can be performed, and flow rate measurement accuracy can be improved.

1 is an overall view showing a configuration of an engine to which a gas flow rate measuring device of the present invention is applied. The figure which shows the structural example 1 and the mounting state of the gas flow sensor of the gas flow measuring device of this invention. Explanatory drawing of a prior art and a subject. The block diagram of the gas flow measuring device of this invention. The block diagram of the flow volume correction system of the gas flow measuring device of this invention. The figure which shows the process sequence of the flow volume correction system of the gas flow measuring device of this invention. The figure which shows the operation | movement at the time of the backflow of the flow volume correction system of this invention. The figure which shows the operation | movement at the time of the forward flow of the flow volume correction system of this invention. The figure which shows the flow measurement error by the flow volume correction system of this invention. The perspective view which shows the structural example 2 of the gas flow sensor of the gas flow measuring device of this invention. The figure which shows the flow volume detection characteristic by the structural example 2 of a gas flow sensor.

[Example 1]
An example of a diesel engine to which the gas flow rate measuring device of the present invention is applied is shown in FIG. Here, the engine to which the EGR control device of the present invention is applied is not limited to a diesel engine, but can also be applied to a gasoline engine that introduces EGR.

  Air taken in by the engine 1 is taken in from an air cleaner (not shown) and is supercharged by the compressor 4A of the turbocharger 4. The intake air amount of the engine 1 is measured by an intake air amount sensor 3 provided in the intake pipe 2.

  The intercooler 5 cools the air supercharged by the compressor 4 </ b> A of the turbocharger 4. The air cooled by the intercooler 5 is distributed to each cylinder by the intake manifold 8 and is sucked into the combustion chamber 19. The intake air amount is controlled by the throttle valve 6. Further, an intake pipe pressure sensor 7 is provided in the intake pipe as necessary.

  A fuel injection valve 9 for injecting fuel into the combustion chamber 19 is attached to the engine 1. The fuel injected into the combustion chamber 19 by the fuel injection valve 9 generates an air-fuel mixture with intake air and burns in the combustion chamber 19.

  The already burned gas (exhaust gas) discharged from the combustion chamber 19 is discharged to the exhaust pipe 10 to drive the turbine 4B of the turbocharger 4.

  An EGR inlet 15 is formed in the middle of the exhaust pipe 10. Part of the exhaust gas (EGR gas) flowing through the exhaust pipe 10 flows from the EGR intake port 15 through the EGR pipe 11 to the EGR cooler 14 and the EGR control valve (EGR valve) 12, and then through the EGR intake port 16 to the intake manifold. Reflux in 8.

  The EGR valve 12 adjusts the EGR gas flow rate. An exhaust gas flow rate sensor 13 (gas flow rate sensor) for measuring the EGR gas flow rate is attached in the EGR pipe 11. A flow rate detection signal (voltage) of the exhaust flow rate sensor 13 is input to the flow rate measurement unit 17. The flow rate measurement unit 17 performs predetermined signal processing on the flow rate detection signal, thereby converting the flow rate measurement signal into a mass flow rate of the exhaust gas, and outputs it to an engine control unit (ECU) 18.

  FIG. 2 shows a configuration example and an attached state of the exhaust flow sensor 13. As shown in the cross-sectional view of FIG. 2, the exhaust flow rate sensor 13 measures the gas flow rate by detecting the heat radiation amount of the heating resistor 30 disposed in the EGR passage 11. Reference numeral 31 shown in FIG. 2 is a resistance temperature detector for correcting the influence of the gas temperature on the flow rate measurement value, and reference numeral 32 is a support portion of the resistor.

  The EGR passage 11 is a gas flow path connecting an exhaust passage and an intake passage, and the exhaust gas in the EGR passage 11 is exhausted in accordance with a differential pressure between the exhaust pressure and the intake manifold internal pressure (intake pressure). Therefore, the flow rate (EGR flow rate) of the exhaust gas that actually flows through the EGR passage 11 fluctuates (pulsates) due to the influence of the exhaust pressure fluctuation and the intake pressure fluctuation. Therefore, in an operating state where the exhaust pressure fluctuation and the intake pressure fluctuation increase, the intake pressure may become higher than the exhaust pressure due to pulsation, and the exhaust (EGR) gas may flow backward to the exhaust side.

  Here, in the side view shown in FIG. 2, the flow of the exhaust gas from the exhaust side to the intake side is a forward flow and the flow from the intake side to the exhaust side is a reverse flow with respect to the exhaust flow rate sensor 13. The exhaust flow sensor 13 measures the gas flow rate by detecting the amount of heat released from the heating resistor (heat wire) 30 due to the gas flow.

  Since the hot-wire flow sensor generally cannot determine the gas flow direction, if a backflow of exhaust gas occurs due to pulsation, it detects this as a forward flow and detects the exhaust gas flow rate more than the actual flow rate. Thereby, the flow measurement error becomes large when the backflow occurs.

  In order to solve such a problem, Patent Document 2 discloses a method for correcting the flow rate detection value due to the back flow by determining the back flow of the hot wire type flow sensor by signal processing. The flow sensor correction method and its problems in the prior art will be described below with reference to FIG.

  In the hot wire type flow sensor, when a back flow occurs due to the pulsation of the exhaust gas, the back flow indicated by the alternate long and short dash line is detected as a forward flow during a back flow period as shown in FIG. When the flow of the exhaust gas changes from the forward flow to the reverse flow, and when the flow changes from the reverse flow to the forward flow, as shown by the solid line in FIG. 3 (b), the differential value of the flow rate detection value changes abruptly. As shown by the solid line in (c), a peak of the second-order differential value of the flow rate detection value is generated.

  Therefore, in Patent Document 2, a period Tr from when the second-order differential value of the flow rate detection value exceeds a predetermined threshold to when the second-order differential value exceeds the threshold again is determined as a backflow period, and FIG. As shown in FIG. 5, the polarity of the flow rate detection value in the reverse flow period is inverted to correct the flow rate detection value.

  Here, in an actual hot wire type flow sensor, the flow rate detection value fluctuates as shown by the broken line in FIG. 3 (a) even in forward flow due to turbulent flow and electrical noise around the heating resistor. At this time, the differential value of the flow rate detection value indicated by the broken line in FIG. 3B varies, and the second-order differential value of the flow rate detection value indicated by the broken line in FIG. Therefore, the second-order differential value exceeds the threshold value, and it may be erroneously determined as a backflow period even in forward flow.

  If the reverse flow period is erroneously determined during forward flow, the flow rate measurement error becomes very large because the polarity of the flow rate measurement value is reversed and corrected. When the flow rate detection value fluctuates due to turbulence or noise, it is difficult to accurately determine the backflow period.

  The gas flow rate measuring device of the present invention is a gas flow rate measuring device equipped with a flow sensor composed of a heating resistor, and even if the flow rate detection value fluctuates due to turbulence or noise, it is possible to reduce measurement errors due to backflow, The exhaust gas performance is improved.

  Hereinafter, the gas flow measuring device of the present invention will be described. FIG. 4 is a diagram showing the configuration of the gas flow rate measuring device of the present invention. The gas flow rate measuring device of the present invention includes the exhaust flow rate sensor 13 and the flow rate measuring unit 17 described above. The flow rate measurement unit 17 includes an input circuit 21 that captures a flow rate sensor signal (voltage), a CPU 22 that is an arithmetic unit, a ROM (reading memory) 23 that stores program processing contents of the CPU 22, and a RAM (RAM that stores calculated data). A memory for writing) 24, and an output circuit 25 for outputting the calculated flow rate correction value. Although the signal of the resistance temperature detector 31 is also input to the flow rate measurement unit 17, the description of the correction of the flow rate due to temperature is omitted.

  FIG. 5 is a block diagram of program processing (signal processing) of the flow rate measurement unit 17. The flow rate measurement unit 17 performs an A / D converter 40 for taking in the flow rate detection signal (voltage) of the exhaust flow rate sensor into the CPU 22 and a correction value calculation for determining whether or not the conditions for calculating the flow rate correction value are satisfied. It comprises a determination unit 41, a differentiator 42 for differentiating the A / D conversion value of the flow rate detection signal, a low-pass filter 43, and an integrator 44.

  Details of the program processing of the flow rate measurement unit 17 will be described with reference to FIG. In step S100, a signal (flow rate detection value Qes) of the exhaust flow rate sensor 13 is taken in every predetermined period ts. The predetermined period ts is set so as to have a relationship of (ts <1 / fs) corresponding to the sampling frequency fs that is twice or more the maximum frequency of the sensor signal according to the sampling theorem.

  Since the exhaust flow rate sensor 13 has a certain response delay in detecting the flow rate, the subsequent calculation processing may be performed on the value obtained by correcting the response delay of the sensor by the advance filter with respect to the flow rate detection value Qes. .

  In step S110, it is determined whether the condition for calculating the flow rate correction value is satisfied (correction value calculation execution determination unit 41). Since the error in the flow rate detection value due to backflow occurs on the low flow rate side of the pulsation, from when the flow rate detection value Qes becomes smaller than the predetermined threshold SL1, until the flow rate detection value Qes becomes larger than the predetermined threshold SL2. A period or the like is a correction value calculation period.

  The threshold values SL1 and SL2 are values obtained by multiplying the weighted average value of the flow rate detection value Qes by a predetermined coefficient (SL1 = 0.8, SL2 = 0.9, etc.) to determine a period in which the flow rate is relatively small with respect to the average flow rate. And

  If it is determined in step S110 that the condition for calculating the flow rate correction value is not satisfied (No), the correction amount calculation in steps S120 to S140 is not performed, the process proceeds to step S150, and no correction is performed in step S150 ( Flow compensation value Qec = Qes). This prevents the forward flow from being corrected by mistake.

  When it is determined in step S110 that the flow rate correction value is calculated (Yes), the process proceeds to step S120, and the process of calculating the differential value of the flow rate detection value Qes is performed. Here, the relationship between the one-dimensional flow velocity differential value dU / dt (the differential value of the soot flow rate) and the passage flow velocity U (the soot flow rate) is expressed by the following equation (1).

  In Equation (1), U is a gas flow rate, ΔP is a passage pressure difference (per unit length), L is a passage length, ρ is a gas density, and Cm is a pipe friction coefficient (per unit length). The first term on the right side of Equation (1) is a term proportional to the passage pressure difference, and the second term is a term corresponding to the pressure loss of the passage.

  Changes in the differential value of the detected flow rate value Qes during backflow will be described with reference to FIG. Here, the response delay of the flow sensor is not considered. As shown in FIG. 7B, the differential value DQ1 of the flow rate detection value Qes immediately before the transition from the forward flow to the reverse flow (immediately before t1) can be set to the flow velocity U = 0 in the equation (1). Is proportional to the pressure difference ΔP in the passage. The passage differential pressure ΔP1 at this time is a negative value, and is a differential pressure in the reverse flow direction. Next, the differential value DQ2 of the flow rate detection value Qes immediately after reversing from the forward flow to the reverse flow (immediately after t1) detects the reverse flow as the forward flow, so the differential value DQ1 has the same absolute value and the opposite polarity ( DQ2 = -DQ1). Therefore, ignoring the response delay of the flow rate sensor, the differential value of the flow rate detection value Qes changes discontinuously when switching from forward flow to reverse flow, and the amount of change in the flow rate detection value Qes (DQ2-DQ1) at this time is reverse flow Proportional to differential pressure ΔP1 in the direction.

  Since the actual flow rate sensor has a response delay, when the response of the flow rate sensor is approximated by a first-order lag, the rising speed (the slope of the arrow) of the differential value of the flow rate detection value Qes immediately after the transition from the forward flow to the reverse flow is changed ( Proportional to DQ2-DQ1). Therefore, the rising speed of the differential value of the flow rate detection value Qes is proportional to the differential pressure ΔP1 in the reverse flow direction.

  As a result of intensive studies by the inventors, it has been found that the passage pressure difference in the reverse flow direction when the flow changes from the forward flow to the reverse flow due to pulsation has a high correlation with the reverse flow rate. As mentioned above, the passage differential pressure in the reverse flow direction is proportional to the rising speed of the differential value of the flow rate detection value Qes, so it is considered that the rising speed of the differential value of the flow rate detection value Qes has a correlation with the reverse flow rate. It is done. Therefore, the gas flow rate measuring device of the present invention is configured to correct the flow rate detection value Qes with a parameter having a correlation with the rising speed of the differential value of the flow rate detection value Qes.

  Here, the rising speed of the differential value of the flow rate detection value Qes has substantially the same physical meaning as the second-order differentiation of the flow rate detection value in Patent Document 2 described above. Since the backflow period is determined by comparing the second-order differential value of the value with a predetermined threshold, the second-order differential value fluctuates when the flow rate detection value fluctuates due to turbulence or noise, and the backflow period It was difficult to determine correctly. When the reverse flow period is erroneously determined, the forward flow is corrected as the reverse flow, which causes a large error in the flow rate correction value.

  On the other hand, in the gas flow measuring device of the present invention, the correction amount is continuously calculated by the differential value of the flow rate, rather than determining and correcting the backflow period by a single change of the differential value of the flow rate. (Because the flow rate detection value is corrected with the correction amount according to the flow rate differential value) The effect of temporary flow rate fluctuations due to turbulence and noise is reduced, and the flow rate is reduced by processing that reduces the effect of flow rate fluctuations. Even if the detected value fluctuates, errors due to backflow can be reduced.

Hereinafter, the flow rate correction method in the gas flow rate measuring device of the present invention will be described in detail.
In step S130 of FIG. 6, a smoothed value is calculated by applying a low-pass filter to the differential value (flow rate differential value) of the flow rate detection value Qes. The low-pass filter calculates the smoothed value of the flow differential value using a weighted average or the like shown in the following equation (2) for each sampling period of the flow rate detection value Qes.

DQF [n] = KLP × (DQ [n] −DQF [n−1]) + DQF [n−1] (2)
In the above equation (2), DQ [n] is the flow differential value, DQF [n] is the current filter calculation value, DQF [n−1] is the previous filter calculation value, and KLP is the filter coefficient.

  Next, in step S140, the flow rate correction value Qec is calculated by integrating the smoothed value DQF of the flow rate differential value, which is the flow rate differential value after the low-pass filter, for each sampling period of the flow rate detection value Qes. Here, the integration of the smoothed value DQF of the flow rate differential value is performed by setting the flow rate correction value Qec immediately before being the condition for calculating the flow rate correction value Qec in step S110 as an initial value. Integration of the smoothed value DQF of the flow rate differential value is performed by the following equation (3) until the condition for calculating the flow rate correction value Qec is not satisfied after the condition is satisfied.

Qec [n] = Qec [n−1] + DQF [n] (3)
In the above equation (3), DQF [n] is a filter calculation value, Qec [n] is a flow rate correction value, and Qec [n−1] is a previous flow rate correction value.

  In step S160, the flow rate correction value Qec is converted into a voltage signal or the like and output.

  FIG. 7 (c) shows a flow rate differential value (annealing value) after the low-pass filter. The dotted line in FIG. 7 (c) is the flow rate differential value before performing the filter process. The low-pass filter can correct the rising speed of the flow differential value according to the rising speed of the flow differential value from the frequency characteristic. That is, as the rising speed of the flow rate differential value increases, the correction amount in the decreasing direction of the flow rate differential value increases. Accordingly, as shown in FIG. 7 (d), the flow rate correction value Qec obtained by integrating the flow rate differential value after the low-pass filter is corrected in the flow rate decreasing direction as the rising speed of the flow rate differential value increases. Is done.

  This flow rate correction method is characterized in that the influence of fluctuations in the detected flow rate due to turbulent flow and noise can be reduced, and that the detected flow rate can be prevented from being erroneously corrected during forward flow.

  FIG. 8 shows the operation of this flow rate correction method during forward flow. When the flow rate detection value Qes fluctuates as shown by the broken line in FIG. 8A, the flow rate differential value fluctuates as shown by the broken line in FIG. 8B. Here, since the fluctuation of the flow rate detection value due to turbulent flow or noise is generally high frequency, when the low-pass filter processing is performed on the flow rate differential value shown by the broken line in FIG. Variability is reduced. In addition, as shown in FIG. 8 (d), the flow rate correction value Qec is calculated by integrating the filtered flow rate differential value, so that the influence of fluctuations in the flow rate differential value is further reduced by the integration process.

  That is, in this flow rate correction method, the effect of temporary flow rate fluctuations due to turbulence and noise is reduced by calculating the correction amount continuously from the differential value of the flow rate. Since the filter processing and the integration processing are performed, the influence of the flow rate fluctuation can be further reduced. Thereby, there is no malfunction of correction due to turbulent flow or noise, and appropriate correction according to the reverse flow rate can be performed.

  FIG. 9 shows the characteristics of the flow rate measurement error when correction is performed by this flow rate correction method. Here, the average flow rate indicates an error characteristic when the amplitude of pulsation is changed under a constant condition. The magnitude of the pulsation (pulsation amplitude ratio) is defined by the ratio of the difference Qpp between the maximum and minimum values of the actual flow rate and the average value Qave of the actual flow rate, as shown in Fig. 9 (a). (Qpp / Qave), as shown in FIG. 9B, when the pulsation amplitude ratio exceeds 200%, a reverse flow is generated.

  As shown by the dotted line in FIG. 9B, the flow rate measurement error characteristic when the correction for the backflow is not performed has a large error in the flow rate increasing direction in the backflow region (pulsation amplitude ratio of 200% or more). On the other hand, as shown by the solid line in FIG. 9B, the flow measurement error characteristic when the correction is performed can greatly reduce the error in the reverse flow region.

  In this flow rate correction method, the heating resistor 30 and the temperature measuring resistor 31 as shown in FIG. 10 are arranged in the bypass passage 51 in order to protect the heating resistor and reduce measurement errors due to pulsation and backflow. The present invention can also be applied to a type of flow sensor. When measuring the flow rate of EGR gas, it is arranged so that the inlet 52 of the bypass passage faces the exhaust pipe side. Here, the outlet 53 of the bypass passage opens in a direction perpendicular to the flow direction of the EGR gas. This is because the forward flow is introduced into the bypass passage, the backward flow is less likely to enter the bypass passage, and measurement errors due to the backward flow are reduced.

  In such a configuration, as shown in FIG. 11, since the backflow flowing into the bypass passage 51 is reduced (attenuated) during the period in which the backflow occurs, the detected flow rate value (the polarity is reversed) ) Decreases with respect to the flow rate of the main passage (EGR passage). Thus, in the method of reversing and correcting the flow rate detection value in the period determined as the backflow as disclosed in Patent Document 2, it is difficult to calculate the backflow rate.

  The relationship between the bypass flow velocity differential value dU / dt (differential value of the soot flow rate) and the passage flow velocity U (soot flow rate) during forward flow is expressed by the following equation (4).

  Like the flow rate sensor of the type in which the heating resistor 30 is arranged in the EGR passage 11, the flow rate differential value DQ1 immediately before the transition from the forward flow to the reverse flow (U≈0) is proportional to the differential pressure of the passage in the reverse flow direction. To do. Similarly, in the flow rate sensor having the bypass passage 51, the reverse flow rate is correlated with the differential pressure of the bypass passage in the reverse flow direction.

  Here, before and after the transition from the forward flow to the reverse flow, the passage pressure difference in the reverse flow direction can be considered to be substantially equal. Since it is possible to detect the passage pressure difference immediately before turning to the flow rate differential value rising speed, it is possible to apply the correction method of the gas flow rate measuring device of the present invention.

  The procedure for calculating the flow rate correction value Qec is the same as the processing in the flow rate sensor of the type in which the heating resistor 30 is disposed in the EGR passage 11 described above.

  According to the gas flow rate measuring device for an internal combustion engine of the present invention, the flow rate detection value of the gas detected by the gas flow rate sensor is differentiated to calculate the flow rate differential value, and the flow rate detection value is calculated with a correction amount corresponding to the flow rate differential value. Since the correction is made, it is possible to reduce the influence of temporary flow rate fluctuations due to turbulence and noise. Therefore, even when the flow rate detection value fluctuates, there is no malfunction of correction, appropriate correction according to the reverse flow rate can be performed, and flow rate measurement accuracy can be improved.

  According to the gas flow rate measuring device for an internal combustion engine of the present invention, the flow rate differential value is filtered, the flow rate differential value is smoothed, and the flow rate differential value is corrected according to the flow rate differential value. Since the flow rate detection value is corrected, the influence of the flow rate variation can be further reduced.

  According to the gas flow rate measuring apparatus for an internal combustion engine of the present invention, the flow rate correction value obtained by correcting the flow rate detection value is calculated by integrating the smoothed value of the flow rate differential value, so that the influence of the flow rate fluctuation can be further reduced. . Therefore, even if the flow rate measurement value fluctuates due to turbulent flow or noise, it is possible to appropriately correct the influence of the backflow and improve the flow rate measurement accuracy. Therefore, the gas flow rate can be measured with high accuracy, and the exhaust gas performance and fuel consumption performance of the internal combustion engine can be improved.

  In addition, this invention is not limited to the above-mentioned Example, A various change is possible in the range which does not deviate from the meaning of this invention. For example, in the above-described embodiment, the flow sensor that measures the flow rate of EGR gas is described. However, the present invention can be applied to a flow rate sensor that measures the flow rate of exhaust gas flowing through an exhaust pipe other than the EGR passage. Moreover, you may apply to the airflow sensor which measures the amount of intake air.

  In the above-described embodiment, the flow correction value is calculated by integrating the smoothed value of the flow differential value, but the flow correction value may be calculated by integrating the flow differential value as it is. .

  The gas flow rate measuring device of the present invention can be applied to various internal combustion engines, and can be applied not only to automobiles but also to marine engines, construction machine engines, and semi-fixed generator engines.

11 EGR passage 13 Exhaust flow sensor (gas flow sensor)
17 Flow measurement unit 18 Engine control unit 30 Heating resistor 42 Differentiator 43 Low-pass filter 44 Integrator 51 Bypass passage Qes Flow rate detection value Qec Flow rate correction value DQ Flow rate differential value

Claims (8)

In a gas flow rate measuring apparatus for an internal combustion engine provided with a gas flow rate sensor for detecting a gas flow rate based on a heat radiation amount of a heating resistor,
A flow rate calculation means is provided for differentiating a flow rate detection value of the gas detected by the gas flow rate sensor to calculate a flow rate differential value, and correcting the flow rate detection value with a correction amount corresponding to the flow rate differential value. Gas flow measuring device for internal combustion engine.   The flow rate calculation means corrects the flow rate detection value in a decreasing direction with a correction amount corresponding to the flow rate differential value when the flow rate differential value rises due to reversal of the gas from forward flow to reverse flow. Item 2. A gas flow rate measuring apparatus for an internal combustion engine according to Item 1.   3. The gas flow rate measuring device for an internal combustion engine according to claim 2, wherein the flow rate calculation means increases the correction amount for correcting the flow rate detection value in the decreasing direction as the rising speed of the flow rate differential value increases. .   The flow rate calculation means performs a filtering process on the flow rate differential value, calculates a smoothed value of the flow rate differential value, and corrects the flow rate detection value with a correction amount corresponding to the smoothed value of the flow rate differential value. The gas flow rate measuring device for an internal combustion engine according to claim 1, wherein:   5. The gas flow rate measurement of the internal combustion engine according to claim 4, wherein the flow rate calculation unit calculates a flow rate correction value obtained by correcting the detected flow rate value by integrating the smoothed value of the flow rate differential value. apparatus.   6. The flow rate calculation unit corrects the flow rate detection value when the flow rate detection value is smaller than an average value of the flow rate detection values. 6. A gas flow rate measuring device for an internal combustion engine as described.   The gas flow rate measurement device for an internal combustion engine according to any one of claims 1 to 6, wherein the gas flow rate sensor has a bypass passage in which the heating resistor is disposed.   The internal combustion engine according to any one of claims 1 to 7, wherein the gas flow sensor detects a flow rate of at least one of EGR gas, exhaust gas, and intake air of the internal combustion engine. Gas flow measuring device.

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